Talk:Wi-Fi How To
From Navas Wireless Wiki
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This system needs about 20 dB more receive power to be feasible. If one could change the back to back antennas to 18 dB antennas, you might make it. | This system needs about 20 dB more receive power to be feasible. If one could change the back to back antennas to 18 dB antennas, you might make it. | ||
| - | Still, the two end terminals here could not be farther apart than the two distances shown, a total of 15 meters. Free space loss at 15 meters is 64 dB, compared to 70 dB for the 18 dB gain back to back antennas if you had them. So if you don't have good isolation from other extraneous reflections and refractions, you may get self-interference that is problematic. | + | Still, the two end terminals here could not be farther apart than the two distances shown, a total of 15 meters. Free space loss at 15 meters is 64 dB, compared to 70 dB for the 18 dB gain back to back antennas if you had them. So if you don't have good isolation from other extraneous reflections and [http://en.wikipedia.org/wiki/Knife-edge_effect refractions], you may get self-interference, maybe [http://en.wikipedia.org/wiki/Picket_fencing picket fencing], that is problematic. Oh Oh, the wikipedia reference does not explain the proper nature or origin of picket fencing. |
A 2x2.5 ft passive repeater, properly aligned, should have a gain of about 50 dB, which is 16 dB better than the two 18 dBi back to back antennas. That 50 dB gain is just what I cranked out here in a spreadsheet, I would believe it when I see it. It assumes a zero degree angle between the incoming and outgoing path, which is obviously wrong. Need to correct by cos(alpha), the incident angle. :( | A 2x2.5 ft passive repeater, properly aligned, should have a gain of about 50 dB, which is 16 dB better than the two 18 dBi back to back antennas. That 50 dB gain is just what I cranked out here in a spreadsheet, I would believe it when I see it. It assumes a zero degree angle between the incoming and outgoing path, which is obviously wrong. Need to correct by cos(alpha), the incident angle. :( | ||
